Taxonomic composition and distribution of free-living nematodes on the Tanakagawa tidal flat, Mie Prefecture

Abstract

Interstitial free-living nematodes play an important role in nutrient cycles and biological production on tidal flats. However, to dates, we have little information on these nematodes on Japanese tidal flats, e.g., on the characteristics of quantitative and taxonomic composition of nematodes. In this study, we examined seasonal changes in the density and taxonomic composition (at the family level) of nematodes, as well their spatial distributions, on a small flat (the Tanakagawa tidal flat, 0.06 km²) at the mouth area of a short river (the Tanakagawa River) along the western coast of Ise Bay, central Japan. Sampling was undertaken at the low water of spring tides June 2013 and also every three months from July 2013 to April 2014. Three sediment samples were collected at each of 13 sampling sites set wholly on the flat, using a core sampler (4 cm in diameter, 20 cm in depth). Through the present investigation, nematodes were identified to belong to 18 families. Dominant nematodes were different among the sites, and four clusters of sampling sites were distinguished for nematodes on the flat based on cluster analysis. Cluster I and II included sampling sites occupied with oxidative sediment, dominated by epigrowth feeders in nematodes. It is showed that seasonal change of nematode assemblages of cluster I was larger than other clusters. Cluster III included sampling sites occupied with reductive sediment containing high organic matter, dominated by selective deposit feeders in nematodes. Cluster IV included sampling sites occupied with rather reductive sediment located close to the water route, dominated by non-selective deposit feeders in nematodes.